Oven-thermometer.



No. 693MB. Patents d Fab. u, I902,

' a. .1. DAY.

OVEN THERMOMETER. (Application filed July 5, 1902.)

(No Model.) 2 Sheets-Sheet I.

1 I Irwenivr:

Witnesses:

we norms PETERS 0a.. FHOTO-UTHQ. WASHINGTON n c No. 693,|l8. Patented Feb. ll, I902. v

G. J. DAY.

0VEN THERMOMETEB. (Applic ation filed July 5, 1901.] (No Model.) 2 Sheets-Sheet 2.

V UNITED STATES PATENT OFFICE.

GEORGE J. DAY, OF BOSTON, MASSACHUSETTS.

OVEN-THERMOMETER.

SPECIFICATION forming part of Letters Patent No. 693,118, dated February 11, 1902.

Application filed July 5, 1901f Serial No. 67,141. (No model.)

Massachuseti s,l1ave invented certain new and useful Improvements in Oven-Thermometers, of which the following is a specification.

This invention relates to oven-thermometers, and has for its object to provide certain improvements therein for increasing their sensitiveness to thermal changes, for rendering them more durable and more capable of withstanding without injury jars due to the careless shutting or slamming of oven-doors on which they are mounted, for simplifying their construction, and increasing their general efficiency.

Reference is to be had to the accompanying drawings and to the characters of reference marked thereon, the same indicating like parts or features wherever they occur, said drawings illustrating different embodiments of my invention.

Of said drawings, Figure 1 represents in front elevation an oven-thermometer. Fig. 2 represents a rear elevation of the same. Fig. 3 represents a partial section on line 3 3 of Fig. 2. Fig. 4 represents a section on line 4 4 of Fig. 2. Fig. 5 represents a lever, the index and index-support detachable from the plate. Fig. 6 represents the expansion-rods detached. Fig. 7 represents a rear elevation ofanothercmbodimentof theinvention. Fig.

8 represents another form of spring-tensioned lever.

Referring to the drawings, and more par-' ticularly to Fig. 1, a indicates a concave plate or casing provided with the apertured ears or lugs a for the reception of screws or fastening devices by means of which it is secured to the oven-door of a stove. The door is usually apertured to receive the convex portion of the casing, so that the concave side is exposed to the interior of theoven. On the convex side is secured a dial (0 having a graduated scale a with the degrees between 200 and 500 Fahrenheit noted thereon and also certain information for the aid ofthe cook. This dial-plate is provided with apertures a to receive lugs or projections on the casing a, and it is held in place by a frame b, secured by screws 1) to the convex side of the casing.

Within the concave portion of the casing there is a thermal device consisting of a spring tensioned lever c, of steel, cast-iron, or other metal having a low coefficient of expansion, and one or more expansion rods or tubes formed of brass, copper, or other material having a high coefficient of expansion. Where the casing is round the lever c is curved; but where the casing is square or angular this lever is straight or angular to conform thereto, as shown in Fig. 7. Preferably, I form said lever with a stiffening-rib 'c', which is cut away, as at 0 near its base 0 the rib 0 extending longitudinally of the lever to prevent its bending or yielding except at the portion 0 which possesses more or less resiliency, and returns the lever to original position when permitted'by the expansionrods. The lever may be formed in two parts, as indicated in Fig. 8, the non-yielding portion being of cast-iron or equivalent material and the yielding portion, which is riveted thereto, beingformedofresilientmetal,as spring-steel. The base a is positioned by a projection a formed on the lever, and by the two lugs a a andis securedin placebyone or more screws 0. The free end'of. the lever is pivotally connected by a link cl with a pointer e. The said pointer projects through an aperture a formed in the casing, and is fulcru med ate on a stud projecting inwardly from a supporting-plate f, secured by screws f f to the interior of the casing a. This plate is cut away, as shown in Fig. 3, or separated far enough from the inner face of the casing to permit the free passage of the link d. The pointer e is bent so as to lie substantially flat upon the outer face of the oasingand to project beneath the frame I) and then over the graduated scale.

One of the reasons for providing the supporting-plate f is that the lever, link, and

pointer can all be secured .to it prior to their being seen red in the casing, this saving much time in the installation of the device and labor in removing or replacing the parts thereof.

It is evident that-I may employ two springlevcrs arranged oppositely and attached to the free end of the pointer, as indicated in my prior patent, No. 652,017, dated June 19, 1900, although for all general purposes one lever is sufficient.

The expansion-rods are indicated as three in number, h, 2 and j, which are pivotally connected at their inner ends and extend in different directions from substantially a common center, like the spokes of awheel. The outer ends of the rods 7t and j are pointed, and they project into sockets hj, formed in the lever c and in the casing a. TheIrod t'is passed loosely through an ear f in the plate or support f, and an adjusting-screw i is passed into said ear to bear against the end of the said rod for the purpose of adjusting the tension of the spring-lever and bringing the pointer to zero. Inasmuch as the ends of the rods 1' and j are against rigid immovable abutments and the end of the rod h rests against the leverc, the said rods h and j constitute a toggle, which is straightened by the expansion of the bar '6, bearing against the knuckle thereof, and the, movement of the end of said bar i is multiplied as it is transmitted to the lever c. In addition, however, to the expansion of the rod '11 the expansion of the rods h andj tends to swing the lever still farther, so that the said lever at the point of attachment or engagement with the rod '1; is caused. to move by the expansion of said bars a distance greater than the total amount of expansion of said bars.

I sometimes form the rods h audj of metal having a low coefficient of expansion, such as cast-iron, and rely upon the expansion of the rod t' being multiplied by the toggle to secure the desired extent of motion of the end of the lever 0. Again, at times I form the rod h of cast-iron or'other equivalent material and use only the rods t and j as expansionbars, although I do not thereby secure as great movement of the lever as where all three of the bars are formed of expansion material.

I do not limit myself to any specific con-.

nection between the inner ends of the rods h, t, and j, although I have shown such connection in the drawings as consisting of coupling m connected to the rod 2', the inner ends of the rods 7t andj being pivoted to said coupling. By this construction and arrangement of parts I secure a maximum movement of the lever c which is much greater than if the rods were arranged to form arcs of a curved ring, as shown in my prior patent. The expansion-bars engage the lever at only one point intermediate of its ends, and therefore I secure the greatest possible leverage upon the lever c to multiply the movement imparted to the pointer.

The thermometer as thus described possesses many additional features of advantage which are apparent upon inspection. All of the movable or expansion parts of the thermometer may be connected together, so as to be secured in the casing or plate by the screws f and c. There are no parts which can be jarred out of place, and the whole apparatus is possessed of maximum durability.

Having thus explained the nature of the invention and described a way of constructing and using the same, although without attempting to set forth all of the forms in which it may be made or all of the modes of its use, I declare that what I claim is- 1. An oven-thermometer comprising a lever, a pointer connected to a free end of said lever, a toggle comprising two rods hinged together and hearing at one end against said lever, and an expansion-rod bearing against the knuckle of said toggle at a right angle to the plane of the outer ends of the toggle-rods, whereby when said rod is expanded, the toggle is straightened and the said lever is actuated to move the pointer.

2. An oven-thermometer comprising a casing, a lever, a pointer connected to said lever, and expansion-rods completely within said casing and directly connected together and one of them engaged with said lever, said rods being compounded whereby when they are expanded, they impart to the lever at the point of engagement a movement greater than the combined expansion of said rods.

3. An oven-thermometer comprising a casing, a lever, a pointer connected thereto, a plurality of expansion-rods completely within said casing and connected together at their inner ends, one ofsaid rods forming part of a toggle and hearing at its outer end against the lever and the others of the said rods bearing at their outer ends against fixed abutments.

4. An oven thermometer comprising a spring-tensioned lever rigidly secured at one end, a pointer connected to the free end of said lever, expansion-rods forming a toggle and bearing at one end against the lever, and at the other end against a fixed abutment, and an expansion-rod hearing at one end against the fixed abutment and at the other end against said toggle. I

5. An oven-thermometer comprising a casing, a spring-lever rigidly secured at one end and stiffened throughout its length except near its said rigidly-secured end, an expansion-rod bearing against the stiffened portion of said spring, and 'a pointer connected to the free end of said lever.

In testimony whereof I have aflixed my signature in presence of two witnesses.

GEORGE J. DAY.

Witnesses:

MARCUS B. IVIAY, E. BATCHELDER. 

